pH meters

[Brad_C]

I know I've mentioned my use of pH meters a couple of times. My 3 digit one (x.xx) was starting to get a bit slow, so I ordered a new probe for it last month ($45). It arrived a couple of days ago.

Turns out that although the original probe was 9 years old (the manufacturer thought I was having them on), it wasn't as slow as I thought and only took some 25% longer to reach a stable reading in pool water. So, given your average pH probe is supposed to last 12-18 months, I thought I'd take some pics and explain how I look after it.

The little bottles that came with the EzDO meter are beaut for that probe, so I fill them from the calibration solution bottles. After a couple of months I dump them into the beakers and refill them with fresh.
The solution in the beakers is left out in the open air. It does evaporate a bit, but it stays within about 0.06 pH, so I use that to calibrate the yellow "cheap and nasty" meter. I also use it to pre-rinse the good one before using the fresh calibration solution.

The yellow meter sits in 30ml of electrode storage solution. When I notice the level below the 30ml line I top it up from a DI squirt bottle. It's not critical, but since I started storing that meter in the solution, I haven't needed to recalibrate it more than once a month. Prior to that I was about to bin it as it was all over the shop.

The secret with the EzDO is it lives in storage solution. After use I give it a quick squirt with DI water, and the cap goes back on. When the pH reading falls outside ~3.75 +/1 0.5pH I replace the solution in the cap. The electrode in the picture is the old one and a bit minced as I accidentally put it into Chloroform a few years ago (wrong beaker) and the plastic didn't do so well.

Because of the storage metodology it really only needs re-calibrating every month or so and even then it's generally within about 0.03pH for zero and span, so still better than the yellow peril e-bay special.

It might sound onerous, but it doesn't take much longer than doing a FAS-DPD test and washing out the bottle, and it's easier for me than trying to colour match the phenol red.
Now I have borates in the pool and it moves like 0.04pH a week, it's also really nice to keep accurate numbers in the log so I can see trends I'd *never* spot with the phenol test.

The calibration solution is stored in a room that sits at 30C +/- 1.5C and lasts well over a year (6 month rated life). The storage solution was bought in 2015 and I've got just under half left. So I've spent less on those than I've spent on test titrants.

 

[kimkats]

Nice write up. Where do you store this? Not many places I could store something open like this without fear of it being knocked over or messed with.

 

[Brad_C]

Nice write up. Where do you store this? Not many places I could store something open like this without fear of it being knocked over or messed with.

I have a granny flat in the back yard. It has my office servers in it, my chem gear and some of the fragile tools. As such it has a little A/C to keep the temperature down. It's well insulated and the heat from the servers stops the temperature from dropping far in winter so it's really quite temperature stable. I keep all my pool test kit in there. Clean and dry.

It also has a lock on the door to keep the little people out. So really quite convenient, particularly as the calibration solutions look like funky cordial.

 

[setsailsoon]

Brad,
I've seen your posts on this before. Thanks for the update. Took me quite a while with less expensive pH meters to train myself on the finer red and purple shades involved with the phenol red test. When I messed with pH probes I'm pretty sure the reason I had calibrations problems was not storing them properly. Now that I've switched to borate buffer I may do some additional trending just to "get to know" my new buffer system.

Can you please provide the model number for your pH meter? The only things that come up under that brand for me are $300+. If that's the case Joyfulnoise and awj22 identified a couple others that cost about the same as your replacement probe or less.

Thanks.

Chris

 

[Brad_C]

The one I really like is an EzDO 6011a. The 'a' is important in that it gives you the extra decimal, but more importantly has an effective temperature compensation. I paid $80 for it back in 2010. So it has cost me about $9 per year. The next 9 years will be a bit cheaper!

I like it because it's immersion rated, so if I drop it I don't lose a meter. My 3 year old did that once, which is why I test the water in the skimmer. Still worth it to teach him to do the ph test for me while I'm doing the others. It also has the Oring sealed storage cap. Another awesome feature.

I was going to buy a new $300 Hanna until I found somewhere locally that stocked EzDO. They special ordered an electrode for me. The place I bought it from stopped selling them years ago.

Of course I'm talking Australian dollars which at the moment are about 2 pints of stout to the USD, so it should be more affordable with real money. You have real dollars, we have real volts.

 

[setsailsoon]

The one I really like is an EzDO 6011a. The 'a' is important in that it gives you the extra decimal, but more importantly has an effective temperature compensation. I paid $80 for it back in 2010. So it has cost me about $9 per year. The next 9 years will be a bit cheaper!

I like it because it's immersion rated, so if I drop it I don't lose a meter. My 3 year old did that once, which is why I test the water in the skimmer. Still worth it to teach him to do the ph test for me while I'm doing the others. It also has the Oring sealed storage cap. Another awesome feature.

I was going to buy a new $300 Hanna until I found somewhere locally that stocked EzDO. They special ordered an electrode for me. The place I bought it from stopped selling them years ago.

Of course I'm talking Australian dollars which at the moment are about 2 pints of stout to the USD, so it should be more affordable with real money. You have real dollars, we have real volts.

Brad,

Thanks much Buddy.,. sounds like it's got a great track record.

Chris